The Honduras Truth and Reconciliation Commission has concluded that the removal from office of former President Manuel Zelaya was a coup.
It said the move was illegal and not a constitutional succession as some of Mr Zelaya's opponents said.
The Commission investigated the events of 28 June 2009, when Mr Zelaya was forced into exile in Costa Rica.
The crisis was triggered by Mr Zelaya's refusal to cancel a referendum linked to presidential term limits.
Point of no return
The chair of the Commission, former Guatemalan Vice-President Eduardo Stein, presented the report to current Honduran President Porfirio Lobos, Head of the Supreme Court Jorge Rivera Avilez and Secretary General of the Organization of American States Jose Miguel Insulza in the Honduran capital Tegucigalpa.
The Commission identified Mr Zelaya's decision to press ahead with the referendum on constitutional change as "a point of no return" in the crisis.
His critics said the move was aimed at removing the current one-term limit on serving as president, and paving the way for his possible re-election - a charge he repeatedly denied.
The consultation was ruled illegal by the Supreme Court and Congress.
When Mr Zelaya insisted the consultation go ahead, Congress voted to remove him for what it called "repeated violations of the constitution and the law".
The Truth and Reconciliation Commission said Mr Zelaya, 58, had manoeuvred himself into a corner, where he lacked the support of Congress, the Supreme Court, and even his own party.
The Commission said Mr Zelaya broke the law when he disregarded the Supreme Court ruling ordering him to cancel the referendum.
It said therefore both Mr Zelaya and those who ousted him bore responsibility for his forced removal from office.
De facto regime
The report said the Honduran Congress lacked a clear procedure to resolve power conflicts such as the one which arose in June 2009 between the president and Congress, but that it had acted beyond its limits by deposing the president.
The report further said that Congress overstepped its powers when it nominated Speaker of Congress Roberto Micheletti as interim president.
According to the Commission, the interim administration was therefore illegal and a "de facto regime".
The report also said that 20 people were killed in the repression which followed the coup.
"At least 12 people were killed by police and military forces making disproportionate use of their firearms and toxic gases," the report added, while another eight opposition activists were killed "by the state or people acting in its interest".
Mr Micheletti led the interim government for seven months, but his administration was not recognised internationally, and the Organization of American States expelled Honduras.
He was replaced by the current President Porfirio Lobo after general elections were held in November 2009.
Many governments, including the United States, restored their ties with Honduras after Mr Lobo's election.
The Truth and Reconciliation Commission was established under the auspices of the Organization of American States to look into the events surrounding Mr Zelaya's removal from power.
Mr Zelaya returned to Honduras in May, but under Honduras' constitution he cannot run in the 2013 election as presidents are limited to a single term in office.